Such a regulating device is known from WO-A1-96/09475. (also DE 44 38 398.9 or U.S. Pat. No. 5,810,565) The descending characteristic curve of the flow rate is attained with this regulating device. In order to make possible different shapes of the characteristic flow rate curve, it is necessary to use different springs and different piston diameters. If, however, a characteristic flow rate curve of an unsteady course is desired, for example of a stepped course, such a characteristic curve can only be realized with an increased outlay, for example by using two successively acting springs.